Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm^–3 (TOA); HF concentration in the feed solution, 0.01 mol·dm^–3 and concentration of NaOH used as stripping agent 2.5 mol·dm^–3. The maximum flux and permeability determined under optimum conditions are 3.06·10^–5 mol·m^–2·s^–1 and 8.44·10^–11 mol· ·m²·s^–1 at 25±2°C and 4.21·10^–5 mol·m^–2·s^–1 and 11.55·10^–11 mol·m²·s^–1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10^–11 mol·m²·s^–1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.     

Selective separation and enrichment of proteins in aqueous two-phase extraction system

A simple aqueous two-phase extraction system(ATPS) of PEG/phosphate was proposed for selective separation and enrichment of proteins.The combination of ATPE with HPLC was applied to identify the partition of proteins in two phases.Five proteins (bovine serum albumin,Cytochrome C,lysozyme,myoglobin,and trypsin) were used as model proteins to study the effect of phosphate concentration and pH on proteins partition.The PEG/phosphate system was firstly applied to real human saliva and plasma samples,some pro...     

Substoichiometric separation using ion-association extraction systems

A theory of ion-association extraction using tetraphenyl-arsonium, triphenylsulphonium and tetraphenylphosphonium ions is given, from which these reagents are shown to be suitable for selective substoichiometric separations. From these considerations it follows that the substoichiometric determination of manganese, rhenium and iodine by activation analysis should be possible; however, the use of these reagents for isotope dilution seems to be doubtful.     

Selective separation of magnolol using molecularly imprinted membranes

Molecularly imprinted membranes (MIMs) for selective separation of magnolol were prepared by thermal polymerization using magnolol as the template, ethylene glycol dimethacrylate (EGDMA) as the cross‐linker, 2,2‐azobisisobutyronitrile (AIBN) as the initiator, organic solvent as the porogen, methacrylamide (MAM) and acrylic acid (AA) as the functional monomers and cellulose acetate as the agglutinant. Commercial filter paper was used as the supporting material. The effects of different porogens and the ratio of functional monomers on the binding and recognition capacity of MIMs were investigated, and the morphology of the membranes was examined by scanning electron microscopy (SEM). The results showed that the MIMs have the highest selectivity to magnolol when the ratio of MAM/AA was 1:4 and tetrahydrofuran (THF) with dimethyl sulfoxide (DMSO) was used as the porogen. The morphology of the imprinted membranes after template extracting is much rougher with big cavities than that of the non‐imprinted membranes (NIMs) and the imprinted membranes before template extracting. The MIMs can selectively separate the magnolol.     

Hydration of tri-n-octylamine hydrobromide and tri-n-octylamine hydroiodide benzene solutions

Isopiestic equilibrations of TOAHBr and TOAHI benzene solutions were made in the concentration range from 0.02 to 0.15 mol/kg at different water activities and 25°C. Limiting hydration numbers of 0.585 ± 0.009 for the bromine ion and 0.340 ± 0.009 for the iodine ion were found at unit water actifity for the systems investigated. The Gibbs-Duhem relation for a ternary system was applied to determine the effects of water activity on the amine salt activity. From the low frequency band in the IR spectra, corresponding to stretching of the “bonded” OH, the hydrogen bond energy between the halide ion and water molecule was evaluated and amounted to: 4.4; 4.0 and 3.4 kcal/bond for the chlorine, bromine and iodine ions, respectively. The isopiestic as well as IR data reveal the following order in proton-acceptor abilities of the halide ions: Cl⁻ > Br⁻ > I⁻.     

Selective flotation-separation and spectrophotometric determination of cadmium using phenanthraquinone monophenythiosemicarbazone.

A simple, selective and sensitive procedure is described for the preconcentration by flotation followed by spectrophotometric determination of trace amounts of Cd(II). Cadmium forms an intense red 1:2 complex with phenanthraquinone monophenylthiosemicarbazone (PPT) at pH > or = 6. The colored Cd-PPT complex was floated quantitatively with oleic acid (HOL) surfactant at pH 6.5, exhibiting maximum absorbance at 520 nm and having a molar absorptivity of 2.4 x 10(5) L mol(-1) cm(-1). The stability constant of the formed complex is 1.5 x 10(12); log K = 12.2. Beer's law was obeyed over the concentration range 0.01-0.34 mg/L. The Sandell sensitivity and relative standard deviation are 0.4 ng/cm2 and 2.6%, respectively. The results obtained spectrophotometrically were compared to those obtained by AAS analysis. The analytical parameters affecting flotation and hence determination have been thoroughly investigated. The proposed procedure was successfully applied to the determination of Cd(II) traces in certified and real human hair samples as well as in natural waters. The structure of the complex formed and the mechanism of flotation were proposed.     

Selective extractive separation of zinc, cadmium and lead from iodide media with mesityl oxide

The extractive separation of zinc, cadmium and lead with mesityl oxide has been investigated as a function of iodide concentration and acidity. The recovery of these metals from the organic phase by back-extraction and the behaviour of other elements under the optimal conditions established for each metal ion have been examined. The method developed has been applied to the separation of these metals from rock samples before determination by spectrophotometry.     

Determination of cadmium,copper and lead in urine by flame atomic absorption spectrometry after extraction of the iodide complexes as ion-pairs with tri-n-octylamine

A simple, rapid sensitive atomic absorption spectrometric method is described for the determination of cadmium, copper and lead in urine. The metals are extracted as their iodide complexes with tri-n-octylamine in n-butyl acetate, without elaborate pretreatment, and measured by direct nebulization of the extract into an air/ acetylene flame. Detection limits for cadmium, copper and lead in urine were 0.008, 0.05 and 0.02 × 10^?6 mol l^?1, respectively.     

Selective separation and reversed phase extraction of zirconium and hafnium from a multitracer solution

The solvent extraction of Zr and Hf was studied using 444-trifluoro-1-(2-thienyl)-1,3-butanedione (TTA) from a multitracer solution containing carrier-free radioisotopes of Zr, Hf, and other elements. The multitracer was prepared from Au foil irradiated with high-energy heavy-ion beams. Effects of HCl and HNO₃ concentrations and organic solvent on the extraction and coextraction of other radionuclides have been studied. It was found that decalin (decahydronaphthalene) was the best solvent among 14 solvents studied and the optimum aqueous phase was 2 mol·dm^–3 HCl or HNO₃. About 2–10% of Sr, Rb, Sc and Nb were coextracted with Zr and Hf. The reversed phase extraction of Zr and Hf was also developed by using ethylenediaminetetraacetic acid (EDTA) solution at pH range of 8.5–10.     

The separation of zinc(II) and cadmium(II) by liquid-liquid extraction

The extraction of Zn(II) and Cd(II) from thiocyanate solutions with bis-2-ethylhexyl sulphoxide (B₂EHSO) in benzene as an extractant has been studied by tracer techniques. For comparison, extraction has also been carried out with tributylphosphate (TBP). The extraction data have been analysed by both graphical and theoretical methods by taking into account complexation of the metal in the aqueous phase by inorganic ligands and plausible complexes extracted into the organic phase. The results demonstrate that Zn(II) is extracted as Zn(SCN)₂·2B2EHSO and Zn(SCN)₂·2TBP. In the case of Cd(II), the extracted species are Cd(SCN)₂·4B2EHSO/4TBP. The synergistic extraction of Zn(II) and Cd(II) with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and B2EHSO or TBP or trioctylphosphine oxide (TOPO) from acetate buffer solutions has also been investigated. Zn(II) is extracted as Zn(PMBP)₂·B2EHSO/TBP/TOPO. On the other hand, Cd(II) is found to be not extracted with these mixed-ligand systems under the experimental conditions. These results also demonstrate the mutual separation of Zn(II) and Cd(II) using the synergistic extraction with HPMBP in the presence of various neutral oxodonors.     

Selective extraction and separation of iron(III) with 4-methylpentan-2-ol

4-methylpentan-2-ol is used for quantitative extraction of iron(III) from 5.5-6M hydrochloric acid. The iron(III) is then stripped with water and determined titrimetrically. Te(IV), Se(IV), ascorbate, fluoride and thiocyanate interfere must be absent. Mo(VI), W(VI) and Au(III) are co-extracted but do not interfere in the determination.     

Electrodialytic separation of cobalt(II) and nickel(II) using liquid membranes based on tri-n-octylamine and trialkylbenzylammonium chloride

Electrodialytic separation of Co(II) and Ni(II) in the course of their transfer from 3–4 M HCl solutions into dilute solutions of various acids using liquid membranes that contain anion-exchange carriers was studied. The influence exerted on the metal transport rate and separation efficiency by the compositions of the feed and receiving aqueous solutions and of liquid membranes and by the electrodialysis current density was examined. Under optimal conditions, in metal recovery from a solution containing an equimolar mixture of 0.01 M CoCl₂ and NiCl₂, the separation factor β_Co/Ni is 147; when nickel in the feed solution is in excess, it reaches 330, and when cobalt(II) is in excess, it exceeds 400.     

Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam

A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction, conditions for the separation of zinc from cadmium, influence of other cations and anions on the zinc sorption by PU foam, and required conditions for back extraction of zinc from the PU foam. The results show that zinc traces can be separated from large amounts of cadmium at pH 3.0±0.50, with the range of thiocyanate concentration from 0.15 to 0.20 mol l⁻¹, and the shaking time of 5 min. The back extraction of zinc can be done by shaking it with water for 10 min. Calcium, barium, strontium, magnesium, aluminum, nickel and iron(II) are efficiently separated. Iron(III), copper(II) and cobalt(II) are extracted simultaneously with zinc, but the iron reduction with ascorbic acid and the use of citrate to mask copper(II) and cobalt(II) increase the selectivity of the zinc extraction. The anions nitrate, chloride, sulfate, acetate, thiosulphate, tartarate, oxalate, fluoride, citrate, and carbonate do not affect the zinc extraction. Phosphate and EDTA must be absent. The method proposed was applied to determine zinc in cadmium salts using 4-(2-pyridylazo)-resorcinol (PAR) as a spectrophotometric reagent. The result achieved did not show significant difference in the accuracy and precision (95% confidence level) with those obtained by ICP–AES analysis.     

The extraction of cobalt (II) from hydrochloric acid solution by tri-n-octylamine

The partition of cobalt (II) between hydrochloric acid solutions and benzene solutions of tri-n-octylamine (TOA) has been investigated under different conditions. The absorption spectra of both the aqueous and organic phases have been examined, and the i.r. spectrum of the organic phase has been studied.     

The extraction of uranium (VI) from hydrochloric acid solutions by tri-n-octylamine

The partition of uranium (VI) between hydrochloric acid solutions and solutions of tri-n-octylamine (TOA) in organic solvents has been investigated under different conditions, and infra-red studies have been made of the organic phase.     

Selective Substoichiometric separation of fluoride by solvent extraction into chloroform with triphenyl-tin chloride

Summary A unique method has been developed for the selective separation of fluoride from a 50% dimethylsulfoxide (DMSO) aqueous phase via Substoichiometric replacement reaction with triphenyl-tin chloride and extraction into chloroform. Precise (±2.5%) Substoichiometric separations of fluoride in the presence of bromide, chloride, iodide, nitrate, thiocyanate, or sulfate have been accomplished. Applicability of the method for radionuclide separations in activation analysis is demonstrated via the examples of irradiated ammonium fluoride, hydrofluoric acid, and¹⁸F isotope labeled sodium and magnesium fluorides. Results for quantitative radioisotope dilution determinations show an error of ±2.1% for a fluoride level of 0.761±0.044 mg.

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Selektive substöchiometrische Abtrennung von Fluorid durch Extraktion mit Triphenylzinnchlorid in Chloroform

Zusammenfassung Die selektive Abtrennung von Fluorid aus 50% igem Dimethylsulfoxid in Wasser durch substöchiometrische Verdrängungsreaktion mit Triphenylzinnchlorid und Extraktion in Chloroform wurde ausgearbeitet. Auf ±2,5% genaue substöchiometrische Trennungen von Fluorid in Gegenwart von Bromid, Chlorid, Jodid, Nitrat, Rhodanid oder Sulfat wurden durchgeführt. Die Anwendbarkeit des Verfahrens für die radiochemische Abtrennung bei der Aktivierungsanalyse wurde an Beispielen von bestrahltem Ammoniumfluorid, Fluorwasserstoffsäure und mit¹⁸F markiertem Natrium-bzw. Magnesiumfluorid gezeigt. Die Ergebnisse der quantitativen Bestimmung der Radioisotop-Verdünnung zeigen einen Fehler von ±2,1% für Fluoridmengen von 0,76±0,044 mg.

     

The extraction of uranium (VI) from nitric acid solutions by tri-n-octylamine

The partition of uranium (VI) between nitric acid solutions and solutions of tri-n-octylamine (TOA) in benzene has been investigated under different conditions, and infra-red studies have been made of the organic phase.     

Selective analysis of histamine in food by means of solid-phase extraction cleanup and chromatographic separation

A simple, practical technique is presented for the selective determination and measurement of histamine (HA) levels in fermented food. The method involved a solid-phase extraction cleanup using a Sep-Pak Plus C-18 cartridge and ion-paired reversed-phase high-performance liquid chromatographic (IP-RP-HPLC) separation, followed by detection of HA at its UV absorbance wavelength of 220nm. After evaporating a methanolic extract from the food sample, the resulting residue was reconstituted with 0.2M phosphate buffer (pH 3.0), and subsequently passed through the cartridge. The aliquot of the solution which came out of the cartridge was chromatographed in IP-RP mode on a C-18 column, as the stationary phase, and with a solution of 0.2M phosphate buffer (pH 3.0)-acetonitrile-water (1:24:166, v/v) containing 2mM sodium 1-octane sulfonic acid, as the mobile phase. When this method was applied to a mixture of HA, Cadaverine (Cad), Putrescine (Put), Serotonin (5HT), and Tyramine (Tyr), only HA was detected at 16.4min of retention time. The method was fully validated and validation parameters were: linearity range 2-1000ppm; correlation coefficient >0.991; mean recovery >99.5%; limit of quantification 2ppm and limit of detection 0.5ppm. The method was next applied to 12 brands of Miso (fermented soybean paste), 9 brands of Sake (rice wine), and 5 brands of Shouyu (Japanese soy sauce) to verify its ability to detect the presence of HA in a variety of fermented foods. The method proved to be both rapid and accurate and is therefore recommended for use in HA pollution surveys and in the routine practice of food-quality control.